It provided few specifics beyond saying the alleged ring promised US visas and residency to educated Iranians in several Muslim countries in a bid to gather information on Iran's infrastructure and its nuclear, aeronautic, defence and biotech sectors.

Iran regularly accuses the United States of seeking to undermine its regime through covert operations.

In 1953, the CIA mounted a coup to overthrow Iran's democratically elected government and install an authoritarian regime headed by a pliant shah.

After Iran's 1979 revolution ousted the shah, and Islamic students subsequently stormed the US embassy in Tehran and took 52 Americans inside hostage for 444 days, the United States cut off diplomatic ties with Iran.

Evidence of part of the US spying programme towards Iran came to light last week when the Islamic republic displayed a US reconnaissance drone it said it had captured.

US President Barack Obama on Monday acknowledged Iran had the drone, a sophisticated and stealthy RQ-170 Sentinel, and requested its return.